
ClassT 3 53 __ 

Book ---C 4A 

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COPYRIGHT DEPOSIT. 



NOTES ON MECHANICAL DRAWING 

Introductory to Machine Design 

Arranged lor Students in the 
LEWIS INSTITUTE 

BY P. M. CHAMBERLAIN 

CHICAGO, ILL. 
1901. 



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•^V^e tiBRARY OF 

CONGRESS, 
Two CoHitfi Received 

NOV. to 1901 

COPVRIQHT ENTRY 

CLASS OJ XXa No. 

/ 'J S ^-j 

COPY a J 



Copyrighted 1901 
by P. M. Chamberlain. 



INTRODUCTORY NOTE. 



It has been the aim for the five years since the Institute opened to 
start the students in machine drawing with as little dependence on text- 
books on drawing as possible, making the instruction largely individual. 
The practice of the best engineering concerns has been constantly scru- 
tinized and the instructors in drawing have felt that some of the practice 
recognized as standard might be put in printed form to the advantage of 
all concerned. Messrs. Moseley, Hatch, Parker, Hawley, Barnay, and 
Barnum, who during this time have given instruction in drawing, 
have contributed suggestions which are embodied in the following 
pages. The tabulations given are few and the student is referred to 
Kent's Mechanical Engineer's Handbook, which should be on the table 
of every engineering student. 

P. M. Chamberlain. 
September, 1901. 



NOTES ON MECHANICAL DRAWING. 



In any drawing-room it may be observed that the instruments act- 
ually used are very few in number. It is therefore advised that the 
beginner start with only those most needed and, if possible, the best ob- 
tainable which are American or American Type Swiss Instruments. 

The celluloid triangles are preferable to all others on account of 
their transparency and cleanliness. One 30° x 60^x90° about 8 inches 
long and one 45^x45^x90° about 4 inches long are convenient sizes. 

The X square should be slightly longer than the drawing board 
and without swivel head. One of good quality pear wood is quite satis- 
factory but more elaborate ones can be had. The head of the T square 
is apt to swell from a true surface where it slides along the edge of the 
board. This may be corrected by occasionally scraping away the bowed 
part. 

The compasses should be the large size supplied with pencil and 
pen legs and adjustable needle point. Large dividers usually come 
with sets but are not very necessary. A set of bow instruments; bow 
dividers, bow pen and bow pencil, complete the necessary tools. The 
last two instruments may be had combined in one instrument whose 
needle point remains stationary while the pen or pencil leg is twirled 
around it. 



This instrument, well made, is, for small circles, preferable to the 
old type of bow instruments. 

The pen usually called the right line pen should be about six 
inches long and with spring blade but no hinge. 



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The catalogs of makers of, and dealers in, drawing instruments 
offer considerable information regarding the construction and care of 
instruments. 

Higgins' water-proof ink is a standard liquid ink but usually is too 
thin when fresh. Evaporation soon brings it to the right consistency. 
Any ink will dry up at the pen point and clog the flow, hence it is nec- 
essary to wipe the pen out frequently with a piece of linen. Scraps of 
tracing cloth washed free from all starch make good pen wipers. It is 
not necessary to change the adjustment of the screw in the pen tc 
clean it properly. 




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The scale should be boxwood, steel, or boxwood covered with 
white celluloid. For machine drawings the proportions usual are 3 in. 
= 1 ft. , whence j:<( in. =: r in. ; i ^ in. — i ft. , whence }i in. = r in. ; or ^ 
in. = i ft., whence 1-16 in. = i in. These divisions are readily found on 
any rule. The triangular architect's scale has these and other divisions, 
and is convenient to have, but troublesome to use, owing to the fact 
that the scale divisions wanted are usually the last found. A four-foot 
folding rule with white background is a most convenient thing to have 
in the pocket and is accurate enough for detail drawings which are to be 
traced. 

For ordinary pencilling the pencil 
should have a long tapering screw- 
driver point, as shown in Figure 2. 
The hardness of the pencil should be 
such as will enable the user to make 
with rapid stokes clear lines which can 
be erased without leaving depressions in the paper. Johann Faber's 
HHHH is recommended for detail paper. 

The drawing-board should have one edge straight and should be 
free from warp and wind. The various constructions can be observed in 
dealers' catalogs. 

For most detail work a white or buff drawing paper with a sharp 
surface is desirable. As pencil drawings are seldom inked-in, the inking 
qualities need not be considered. It is desirable to have sizes of draw- 
ings conform to some standard. Where large quantities are consumed 
the paper is usually bought in rolls and a set of dimensions which may 
easily be remembered, and which cut to advantage, is preferable. If 36 
inch paper is used, a standard of 24 inches by 36 inches is suggested* 
This may be doubled or divided into 2, 4, or 8 parts for smaller sizes, as 
shown in Figure i. 



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with much handling. The line of full size should b 
on the blue print where to trim. 



Inside of the dimen- 
sions thus formed always 
lay off a border line 3/^ 
of an inch from the 
edge. In making a trac- 
ing it is desirable to al- 
low the cloth extra mar- 
gin outside of the full 
dimensions of the stand- 
ard as the edges of the 
tracing become curled 
drawn to indicate 



Standards for center lines, dimension lines and witness lines are 

found in some variety. Red ink lines which print faintly are sometimes 
used for each, but fine black lines with distinctive characteristics are for 
many reasons preferable. A dot and a dash for center lines, two dots 
and a dash for dimension lines, several dots and a full line for witness 
bnes should be used in drawings made in connection with these notes- 
See page 6. Arrow heads should be large enough to indicate 
readily to what the dimension refers and may be made free hand, the 
width being about one-third the length. When the space for a dimen- 
sion is too small to admit the arrow heads and dimension, the arrow 
heads may be placed pointing toward each other and the dimension 
placed outside. 

In making a tracing it is usually best to ink-in first the small 
curves, then the larger ones, and then the straight lines, as it is easier to 
join a large curve or a straight line to a small curve than vice versa. The 
neatness of a tracing depends to a great extent on getting good tangen= 
cies. For those who cannot judge the proper junction with their eye it 




F-IG.3 

is advisable to draw a pencil line through the centers of the two curves, 
as shown in Figure 3, thus determining where they shall come together. 
In joining a curve to a straight line, the center used should lie on a 
perpendicular from the end. In joining a straight line to a curve, it 
should form a right angle with a radial line drawn to point of contact. 

The making of compound curves is usually done with an "irregu- 
lar curve," a scroll with a great variety of curves and seldom the one de- 
sired. The more satisfactory and quite as rapid method is to sketch 
in free-hand the desired curve and then locate sufficient centers to draw 
the curve with the compasses. See also in Figure 3. Greater 
economy of time -may be had by tracing the curve free-hand but this 
should not be attempted until the more exact method is properly 
achieved 

In all drawings of cast parts there should be shown a fillet where- 
ever there are two parts coming together at an angle. These should be 
made with a bow pen or bow pencil. 

Cylindrical pieces are shown in section only when there is internal 
arrangement requiring it. All cylindrical surfaces and circles should 
have center lines indicated. The material to be used in construction 
may be indicated by some convention in cross-sectioning, but economy 
of time and clearness of expression are better served by using plain 



hatching for all materials, and indicating by note, word, or initial the 
material. Where several pieces in contact are shown in section the 
hatch lines may contrast in direction or spacing if necessary, but always 
at forty-five degrees. Lines used in hatching should ordinarily be 
about 1-16 of an inch apart and as fine as the pen will properly make. 
There are many ingenious devices to facilitate equal spacing, but it is 
usually preferable to space by eye. 

When a piece is to be machined or finished and it is not entirely 
obvious that such is the case, it ^ ^ 

is usual to place two letters i7 "tr 

along the projection of the finished surface. When parts are to be fin- 
ished all over they may be marked f=inish a.l.i_ over. 

The location of a dimension should always be such as will 
readily catch the eye of the mechanic and avoid all probable chance of 
confusion. The study of how a piece should be made in the shop is in- 
dispensable to good judgment in this very important consideration. 
This supposes that a designer is capable of directing every step of con- 
struction of that which he designs, as indeed he must be, to produce 
good designs and clear drawings. To be complete, a drawing must 
contain all dimensions and answer all questions that might arise to pat- 
tern maker, blacksmith, or machinist. Dimensions of more than 24 
inches are usually expressed in feet and inches thus : 38" should be 
written 3' — 2". 

In lettering, the letter used should be one that can be quickly 
made, neat, and very easily read. For ease of acquirement and sim- 
plicity, the gothic letter, so called by printers, is satisfactory. Where a 
large letter is required, the following method will be found useful for 
making precise, uniformly spaced letters. See Figure 4. Lay off a line 

for the top limit of the 
legend and beneath it 
a point at a distance 
equal to the desired 
height; divide this 
space into five equal 
parts by the eye. The 
first trial will likely 
be unsuccessful but a 
few trials should bring 
success. Through 
these points, or short 
F"IG..^ lines, draw lines par- 

allel to the top one. With the /!^^ degree triangle lay off oblique lines as 
shown. Take care that the angular lines meet exactly at the top and 
bottom lines. Allowing seven spaces for all letters excepting I, one 




space between letters and four between words, calculate the total num- 
ber of spaces needed and from the middle of the space allotted for 
the words, count to the left half the total spaces and begin laying off 
the upright lines of the letters at the intersection of the oblique with 
the parallel lines. This forms the outline of block letters which can 
easily be supplied with curves, the same centers serving for the inside 




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and outside curves. On page ii is given the construction of all letters 
and figures of this scheme, and the same plan of spacing may be applied 
to the five space letter below. The word "letters" is given above 
in three sizes having exactly the same proportion, the smallest 
exhibiting what should be used for free-hand letters, which are made 
with the right line pen held upright and so adjusted that the width 
of the line is the same whichever direction the pen is moved, the pen 
not being turned from the position used for drawing horizontal lines. A 
standard height of 3-32" for all ordinary notes and dimensions is found 
desirable. 




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When the dimension of a radius is given it should be followed by 
the word radium or abreviation rad. The arrow head should be 
placed at the outer end only, and if it is not evident where the center is, 
a very small circle may indicate it. The dividing line in a fraction 
should always be horizontal. Dimensions should read in the direction 
of the dimension line and from the bottom or right hand side of the 
sheet. 

All parts shown threaded or tapped are understood to be the U. S 
Standard for the size shown unless otherwise stated. The screw threads 
known as V shape. Sellers' or U. S. Standard, square and Powell 
will be here considered. The U. S. Standard is perhaps the most widely 
used, although the V thread is frequently found in commercial bolts, set 
screws and machine screws in the smaller sizes. Where the screw is 
used to transmit power, the square thread or the Powell thread should 
be used. The Powell thread has the advantage that the lash caused by 
wear may be corretced by closing up the nut. 



The V thread has an angle of 60 
degrees between sides of the thread. 
The depth of the thread is .866 of 
the pitch. See Figure 5. 



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The Sellers' thread has an angle 
of 60 degrees between threads. The 
top of the thread and the throat of the 
space are flattened one-eighth of the 
pitch. The depth is .6495 of the pitch. 
See Figure 6. 

The square thread has a profile consistent 
depth is one-half of the pitch. 

The Powell thread has an an- 
gle of 29 degrees between the sides 
of the threads. The depth of thread 
is one-half the pitch. The flat is 
.3707 of the pitch. See Figure 7. 

The term pitch means the dis- 
tance the screw would travel longitudinally during one rotation, but is 
more frequently used to denote the distance from one point on a thread 
to the corresponding point on the profile of the adjoining one. The term 
is sometimes used to mean the number of threads per inch. The term 
is used in these notes with the second meaning. 

In preparing to draw any style of thread, first lay out the limiting 
side lines and center line. Draw light cross lines at a distance apart 
equal to one-half of the pitch. 



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For the Sellers' thread, divide one of these spaces into four parts 
with the aid of the triangle, as in Figure 8 , or by the eye, and draw 




F-IC3.S 

across the figure a line through the proper point which is one-eighth of 

the pitch. With the 30 degree triangle draw the Outlines of one side of 

a thread through the intersection .of the last drawn cross line and the 

limiting side line; this will fix the position of the root lines. Points are 

thus fixed by intersect'ons for all the threads. 

To draw the Powell thread, lay 
off cross lines as before and root 
lines which may easily be located 
by aid of the 45 degree triangle. 
See Figure g. With the two tri- 
angles obtain 15 degrees, this be- 
ing near enough to the actual 14^- 
degrees. Draw through the limit- 
ing lines, and the cross lines all 
the sides of threads corresponding 
to this position. In a similar way 
draw the other sides through the 
intersections of the cross lines and 
F~IG.9 ^^^ '■^^^ lines. 

To draw the helix, locate points 

and whittle a templet from thin hard 

wood. To transfer the points to the 

wood, lay the wood against the 'edge 

of the T square just below the points. 

and with bow dividers measure the 

points,off on the templet. The points 

may be determined by dividing a 

semi circle and half the pitch, into 

equal parts and finding the intersections of the projected divisions as ia 

Figure 10. It is usually sufficient to obtain points from divisions of 

1-16, ys, 5^, }4, ^, 74,, and 15-16 of the semi-circle and rise. 





F=-|C=i. 10 



R.M. single: 



On double threads the profiles on opposite 
sides of the screw are exactly opposite, in 
single threads a depression is opposite a full 
profile. See Figure II. The lines representing 
the helical curves connecting the profiles are 
usually drawn straight. 

It is seldom necessary to detail threads in 
this way and therefore certain conventional 
threads are used. The convention shown in 
Figure 12 may be used for sizes of 3^" or lar- 
ger. For sizes S/g" to %", see Figure 13. For 
sizes under ^i" see Figure 14. 






siMGLE double: uii^oJ LDcd f^'Gi- 

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For drawing a detail of the standard hexagon nut, strike a tempor- 
ary circle equal to the short diameter and with the 30-degree triangle 
put in the hexagon, projecting from it the two elevations. The chamfer 
marked C in the front elevation has no adopted standard but may be 
made 1-12 H in good proportion and at an angle with the horizontal of 
30 degrees. See Figure 15. The projection of this chamfer gives the 
circle on the plan and it in turn ,the chamfer for the narrower elevation 
which is, of course, also 30 degrees. The height of the curves is located 
with a little ingenuity. The proportions for height and short diameter 
are also shown in Figure 15. 

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Fl<3. 15. 



For drawing conven= 
tional nuts the curves may 
be drawn with the diame- 
ter of the bolt for a radius, 
and for the broad projec- 
tion this radius may be used 
to get the approximate 
width. The narrow pro- 
jection of the nut is approx- 
imately i^ times the diam- 
eter of the bolt. 



Sizes of U. S. Standard threads, nuts and bolt heads are given with 
other data on page i6. 

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Set screws usual- 
ly have heads equal 
in diameter and thick- 
ness to the diameter 
of the screw. The 
various forms of 
points are shown in 
Figure i6. 




OVAL. 
POINT 




FT.AT CONICAL HEIADLESS 
POINT POINT POINT 

FIG. 16 



Cap screws vary in proportion by different makers, but there is 
given on Page 17 a table compiled from the Chicago Screw Company's 
catalog. Up to i" diameter they are threaded ^ the length under the 
head, except the flat head which is threaded to the head. 



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In indicating a threaded hole use the convention shown in connec- 
tion with the 5-16" X 1" set screw on page 6, which is simple and clear. 
In cases where the screw is not shown, or where only an end view is 
given it should be marked xar 2", etc. 

Where the material is shown in section as in connection with the 
-y8"x^" set screw on page 6, the threading of the casting is indicated. 
Where it is desired to indicate that the casting is not threaded, a clear- 
ance shown between screw and casting accomplishes it. 

When duplicate parts are required, mark the drawings 2 CDF^ 

THIS or 3 OF= THIS, Or MAkCE 2 or IVIAKE 3, etc. 

When a taper is required the drawing should be marked with the 
taper per foot of length; thus a taper of ^" per foot means a total 
decrease of diameter or width of %" for each foot of length, and in that 
proportion for shorter lengths. When a taper is determined by given 
dimensions at each end of a given length, the approximate taper per 
foot should be given and marked arf=f«ox. xarer. 

Mark all cast parts with a pattern number consisting of the draw- 
ing number followed by a distinguishing letter as shown on page 6. 

LEWIS INSTITUTE 



DATE 

scale: 

1 

The title, drawing number, date, etc., should be in the lower right 
hand corner, lengthwise of the sheet. See Page 6. The number should 
also be placed in the upper left hand corner upside down so that in look- 
ing over a pile of drawings for a certain number, it can be readily found, 
even though some of them may be upside down. The title should ordi- 
narily state first the firm name; second, the machine or structure to 
which the drawing pertains; third, the distinctive title of the particular 
drawing; fourth, the date; fifth, the scale; sixth, the serial number of the 
drawing. Those parts of a title which occur on every drawing should 
be of a standard style and size. This may be obtained by having the 
tracings printed on a press, by using a rubber stamp, or by having a 
copy which can be copied or traced. A rubber stamp does not give an 
impression that will print well and should be filled in with ink if used 
on a tracing. The title used at Lewis Institute is shown in Figure 17. 

The tabulations on pages 16 & 17 give examples of work that 
students may indulge in to great improvement of their skill in. making 



figures and letters. The ability to do neat lettering is of prime import- 
ance to a draftsman. 

In tracing, the picture lines should be nearly 1-32 of an inch wide 
and cross section, witness, centre, dimension, and dotted lines as light 
as can be neatly made. Arrow heads should be distinct and quite acute. 
All lettering and dimensioning should be distinct and uniform in size. 
The drawing pen should be used for making figures and letters. The 
glossy side of the tracing cloth should be used, and well chalked before 
inking. 

In case of necessity of erasure, use a piece of talc crayon to restore 
gloss to the cloth. Never use a knife to erase as the ink will soak into 
the cloth where this is done. A tracing should not be commenced until 
the pencil drawing is complete and checked. 

Figure 18 shows a free hand sketch of a head stock and exhibits 
a class of accomplishment which every draftsman should cultivate. A 
preliminary sketch thus made gives all data necessary for the production 
of a mechanical drawing. 




F=^IO. IS. 



DEOIMAL EQUIVALENTS OF FF=lAOTIONS. 



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A. H. ABBOTT & CO 

...DRAWING MATERIALS... 

48 MADISON STREET, CHICAGO. 

BETWEEN STATE STREET AND WABASH AVENUE. 
XEUE:i=MC3IME MAIN 2429. 



Mathematical 
AND Surveying 

IXSTKUMENTS 




SUPPLIES FOR Schools 

AXD Architects, 

Civil and Mechanical 

Engineers. 





KEUFFEL & ESSER CO. 



OF NEW YORK- 



DRAWING MATERIALS 



SURVEYING INSTRUMENTS 



III E. Madison Street, Chicagfo. 

Between Clark and Dearborn Sts. 



LIBERAL DISCOUNTS TO STUDENTS. 

L.efC. 83 



GEM UNION INSTRUMENTS 



SUPERIOR TO ALL OTHERS IN 



GonstriiGi.lon, Mim\ and Flnlsn. 




"UNION" 
PIVOT 
JOINT 

Strongest and most durable joint made. Warranted to last a lifetime. 
Most complete assortment of 

DRAWING MATERIALS 

IN THE WEST 

EUGENE DIETZGEN COMPANY 

181 MONROE STREET, CHICAGO 
Catalogue on application. 



fnO V :dD iii<il 



NOV 18 1901 

H. & C. WOLFE 

776 W. Madison St. 

Lewis Institute Building 

DEALERS IN 

•..•Oraw^ing* In^truirtGnts.... 

AND MATERIALS 



Such well known makes of Instruments as ALTENEDER'S and DEITZQEN'S 
carried in stock. 

Our prices are always a little lower than down town. Reinember wc 
are rii^Jit in the Lewis Itistitiite Buildiuz. 



You need a keen cutting Knife 
in your work. 

We carry some of the world's best brands — 

Geo. Wo^tGTitiolm^^ 
Jos* Rodgers & Son 's 
and J^mpirG Knife Oo* 

We carry all the standard tools for Manual Training 
Schools. 

Sheldon's Rapid Acting Vices, 
Work Benches, Etc. . . . 

ORR & LOCKETT HARDWARE CO. 

71=73 RANDOLPH STREET, CHICAGO. 




